The Technological World

Humans have always invented and produced objects that have helped them survive and live more comfortably. Today, technology is fundamental to the entire process of designing, manufacturing, maintaining, and repairing objects and systems. ST EST AST

Chapter 12 Manufacturing Technical Objects There have been many inventions that have improved the quality of our lives. We will refer to these inventions as technical objects. A number of issues must be considered when designing and manufacturing these technical objects. In this chapter we will look at: 1. Materials and their properties 2. Technical Drawings 3. Manufacturing of the objects ST EST AST

1. Materials All technical objects are made of materials A technical object must be designed to withstand the constraints and deformations that it experiences during its normal use. ST EST AST

1.1 Constraints and Deformations Constraints are the different types of stresses that a material experiences as a result of the forces applied to it. ST EST AST

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Deformations

Depending on the constraint, the material can undergo three types of deformation. ST EST AST

1.2 Properties The mechanical properties of a material determine how it will deform when subjected to one or more constraints. ST EST AST

Other properties of a material are listed below ST EST AST

1.3 Degradation and Protection The degradation of a material is the decline in some of its properties due to the effects of the surrounding environment. The protection of a material is the application of procedures that prevent or delay its degradation. ST EST AST

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2.Categories of Materials and their Properties Let’s have a closer look at the following materials and their properties: 1. Wood and Modified Wood 2. Ceramics 3. Metals and Alloys 4. Plastics 5. Composites ST EST AST

2.1 Wood and Modified Wood Wood is a material obtained by harvesting and processing trees. Hardwood comes from deciduous trees such as maple, oak, and birch Softwood comes from coniferous trees such as spruce, pine and fir. ST EST AST

Solid Oak Furniture

Oak Flooring

Maple Baseball bats

Properties of Wood The mechanical properties depend on the type of wood and vary due to: 1. The species of tree 2. The speed of growth 3. The water content of the wood Other properties of wood that may influence the choice of this material include: 1. Aesthetic appeal 2. Hardness, elasticity, resilience, and toughness 3. Low thermal and electrical conductivity 4. Ease with which it can be worked 5. Its colours 6. Its lightness relative to its strength ST EST AST

Modified Wood  Modified wood is treated wood or wood made from wood mixed with other substances.  Common products include plywood, particle board and fibreboard  These are sheets, chips, or fibres of wood that are glued together in sheets. ST EST AST

Particle Board

Degradation and Protection of Wood Unprotected wood can degrade swiftly. Since wood is an organic substance, many fungi, microorganisms, and insects can infest the wood, feed off it and cause it to rot. Wood can be painted, stained, varnished or treated with other protective coatings to help prevent its deterioration. Treated wood is made resistant to rot by:  Dipping it in an alkaline solution containing copper. This wood usually has a greenish colour.  Heating it to a high temperature. Some woods, such as cedar, have a natural resistance to rot. ST EST AST

Treated wood

Cedar Docks and Decks

Ceramics

2.2 Ceramics A ceramic is a solid material obtained by heating inorganic matter containing various compounds, usually oxides. When the raw material is heated, the water evaporates, and the bonds between the constituent compounds are rearranged. A ceramic is always solid at room temperature. ST EST AST

Traditionally, most ceramic objects were made out of clay and sand. Sand is used for making glass. Although other materials are now used, clay and sand are still widely used as they are both plentiful and inexpensive. ST EST AST

Properties of Ceramics The properties of ceramic objects vary with the raw material and the method of baking. The following properties make ceramics a good choice for many objects:  Low electrical conductivity – used as insulators  High degree of hardness – used as building materials and cutting tools  Heat resistance and low thermal conductivity – dishes and cookware as well as thermal insulators  Resistance to corrosion – used in ducts for fumes or water  Fragility – most are very fragile, but some can be made so resilient they are used in engines ST EST AST

Ceramics can be fragile

The Degradation and Protection of Ceramics Although ceramics are generally very durable, some acids and bases can have a degrading effect on them Archeologists have found ceramic pieces that are thousands of years old and are still in remarkably good condition. Glazes can be used to protect the ceramics A thermal shock (a sudden change in temperature) can cause damage to a ceramic object. ST EST AST

2.3 Metals and Alloys A metal is a material extracted from a mineral ore. Metals are usually shiny in appearance and are good conductors of heat and electricity. The pure metal is rarely used. An alloy is a mixture of a metal with one or more other substances, which may be metallic or nonmetallic. The mixture of materials results in more desirable properties. ST EST AST

Metals and Alloys

Alloy Bike Frames

There are two main types of alloys:  Ferrous alloys whose main component is iron.  Nonferrous alloys whose main component is a metal other than iron ST EST AST

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The Degradation and Protection of Metals and Alloys The main cause for metal and alloy degradation is oxidation, where the material reacts with oxygen. This is commonly referred to as rusting. The material can be protected by coating it with a substance that isolates it from the oxygen in the air:  Metallic coatings: zinc, chrome, gold, silver, nickel, aluminum, lead  Other coatings: paint, enamel, grease, resin ST EST AST

Oxidation of Metals

Rustproofing

Techniques That Enhance the Properties of Metals and Alloys Steel heat treatments are methods of enhancing certain mechanical properties of steel through periods of heating. These methods include:  Quench hardening – hardens the steel  Tempering – hardens the steel  Annealing – returns the original properties by removing the stress created by deforming (welding) All of these methods work by rearranging the crystals within the material ST EST AST

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Plastics

2.4 Plastics Plastics are made from fossil fuels (petroleum and natural gas) Monomers are extracted from the fossil fuels and are arranged into long chains called polymers. Plastic is a material made of polymers, to which other substances may be added to obtain certain desirable properties. The invention of plastics lead to a revolution in world of materials ST EST AST

Types of Plastics A thermoplastic is a plastic that becomes soft enough when heated to be molded or remolded and that hardens enough when cooled to hold its shape.  Most plastic objects are made of this type.  Most thermoplastics can be recycled A thermosetting plastic is a plastic that remains permanently hard, even when heated.  Often harder and more resilient than thermoplastics  Include melamine and polyesters  Cannot be recycled in Quebec ST EST AST

The Degradation and Protection of Plastics Plastics tend to degrade over time. This process is usually slow, but can be detected as cracks and changes in colour appear. ST EST AST

Composites

2.5 Composites A composite is formed by combining materials from different categories to obtain a material with enhanced properties. A composite has two main parts: the matrix and the reinforcement. The matrix is the body of the material. It surrounds and supports the reinforcement and gives the object its shape. The reinforcement is inserted into the matrix to strengthen the object. ST EST AST

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Kevlar is a composite

The Degradation and Protection of Composites The degradation of composites usually takes one of two forms: 1. The deformation or fracture of the matrix or the reinforcement. 2. The loss of adherence between the matrix and the reinforcement. The speed of degradation depends on the type of matrix and reinforcement and the conditions of use. ST EST AST

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3. Technical Drafting Before a technical object can be manufactured, its shape and dimensions must be determined. A technical drawing must be created. Technical drawings can be made by hand or on a computer. To understand these drawings, we must be able to recognize and analyze different projections. EST AST

3.1 Projections A projection is the representation of a three-dimensional object on a two- dimensional surface. Two of the most commonly used projections are: 1. isometric 2. multiview. EST AST

Isometric or Orothogonal Projections A drawing is an isometric projection if the lines representing the length, width, and height make angles of 60° or 120°. EST AST

Multiview Projections In a multiview projection, each face of the object is drawn separately looking at it from straight on. Usually only the top, front and right side of the object are illustrated. EST AST

Isometric projections show the object in perspective. It represents the three dimensions of the object in a single drawing. Multiview projections usually provide greater detail without distortion. EST AST

3.2 Engineering Drawings A general arrangement is a technical drawing representing the overall appearance on an object. It usually includes the top, front, and right side multiviews as well as an isometric projection drawn to scale. The general arrangement will also include a title block showing important information about the object EST AST

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Exploded Views An exploded view is a drawing in which the various parts of the object are separated from one another so as to more easily visualize the component parts of the object. The drawing will use an isometric projection drawn to scale. The is accompanied by a list of parts indicating their names and the number of each part required. EST AST

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Detail Drawings A detail drawing is a drawing specifying all of the relevant information for manufacturing a part. It is almost always drawn to scale. EST AST

Scale in Drawings 1:1 object is drawn life size 1:2 reduced scale (drawing of object is ½ of its actual size, also 1:5, 1:100 etc)  1 cm on drawing is 2 cm in real life (1:2)

Scale in Drawings 2:1 enlarged scale (a small object is drawn larger than in real life, also 5:1, 100:1 etc)  5 cm on drawing is actually 1 cm in real life (5:1)

Dimensional Tolerances Since machines, tools, instruments, and the operators of machines are not perfect, the manufactured parts may be slightly different from the dimensions indicated on the drawing. A dimensional tolerance is an indicator of the maximum acceptable difference between a specified measurement and the actual measurement on the finished object. EST AST

If the dimensional tolerance applies to all of the parts on a diagram, it may be indicated in the title block. It can also be applied to a single part and indicated as shown in the diagram. EST AST

Functional Dimensioning The functional dimensioning of a drawing specifies the information required for the object to work. For example, the play required for a blade to slide freely in a utility knife is shown as the space between the blade and the guide. EST AST

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Developments A development is the representation of the surface area required to make a part by bending. Sheet metal is often used to manufacture a technical object. The development shows the surface area of the material as well as the lines where the sheet will be bent. EST AST

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3.3 Diagrammatic Representations A diagram is a simplified representation of an object, a part of an object, or a system. Diagrams are used to help explain an object’s operating principals as well as any other characteristics that must considered during the manufacturing process. Depending on the type of information that a drafter wishes to display, one of the following common diagrams will be chosen:  Design Plan  Technical Diagram  Circuit Diagram AST

The Most Common Types of Diagrams AST

Standardized Symbols In Diagrams AST

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4. Manufacturing: Tools and Techniques Once the materials have been chosen and the plans have been drawn, the object must be manufactured. Manufacturing is a series of operations resulting in the creation of a technical object. The various steps in the manufacturing of an object require the use of various instruments. EST AST

A tool is and instrument used in the manufacture of an object. A hand tool is powered by human force. A machine tool is powered by forces other than human. The manufacturing process is usually divided into three parts: 1. Measuring and laying out the parts 2. Machining the parts 3. Assembling and finishing the parts EST AST

4.1 Measuring and Laying Out The information needed for the manufacturing of an object can be found in the detailed drawings of the object, or on its manufacturing process sheet. The manufacturing process sheet is a document describing a series of operation to perform in the manufacturing of a given part and listing the materials and tools required. EST AST

Measuring out is the act of determining the size or position of a marking. Laying out is the act of tracing markings or reference points onto a material. EST AST

4.2 Machining Machining consists of shaping a material into a desired configuration. The first step in machining a part is to cut it out roughly into its approximate shape. The most commons techniques used in this step are cutting, drilling, tapping, threading, and bending. EST AST

Cutting consists of giving a material a desired shape. Drilling consist of making a hole in a material. Tapping is a machining technique in which screw threads are formed inside holes drilled into a material. Threading is a machining technique in which screw threads are formed around a rod. Bending is a machining technique in which a material is curved into a certain shape. EST AST

Inspection Throughout the machining phase, the parts are measured and inspected to ensure that they match the required specifications. AST

4.3 Assembling and Finishing Assembling is a set of techniques by which various parts are united to form a complete technical object. Techniques used for assembling include: nailing, screwing, bonding, riveting, bolting, and welding. Finishing is a set of techniques that complete the manufacture of the parts of a technical object. The finish protects the materials from the elements and enhances the appearance of the object. Finishing techniques include: painting, vanishing, staining, and polishing. EST AST

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Review Observatory: The Environment  Page 421, Review Questions A to D Credits  All images are from: Observatory: The Environment Editions du Renouveau Pedagogique Inc